The disclosed technology relates to a lubricant suitable for a motorcycle that does not have a clutch lubricated by the same lubricant, e.g., with non-lubricated (“dry”) clutch plates.
Lubricants for motorcycles typically provide lubrication for the engine (a crankcase) and a wet clutch. These two devices, although often lubricated by the same fluid, often have different lubrication requirements. For example, the lubrication of the engine desirably provides low metal-on-metal friction, to promote good fuel economy. (Typically, the “metal” referred to is steel.) However, the friction coefficient for the metal-on-composition interfaces located within the wet clutch is typically desired to be relatively high, to assure good engagement and power transmission. Additionally, motorcycle lubricants will also lubricate other devices such as gears or bearings, each having their own lubricating requirement. Many lubricants have been designed over the year for lubrication of motorcycles (also known as motorbikes or motorscooters). One such lubricant is described in U.S. Patent Publication 2008-0096778, Breon et al., Apr. 24, 2008.
Because of the varied and demanding lubrication performance required of them, motorcycle lubricants are typically designed specifically for use in motorcycles. That is, typical lubricants as used in lubricating passenger car engines are not normally used for motorcycles. Such lubricants may exhibit a low coefficient of friction that is undesirable for lubricating the wet clutch found in most motorcycles. The two types of lubricant technologies have, simply put, diverged in recent years.
Nevertheless, there are a certain number of motorcycles which do not employ a wet clutch, but, rather, “dry” or non-lubricated clutches or clutch plates. (Likewise there might be motorcycles for which a wet clutch is lubricated by a separate lubricants from that used to lubricate the engine.) For those motorcycles, the high metal-on-composition friction is of no benefit to the engine and is indeed undesirable to the extent that it may interfere with the provision of the lowest possible friction in the metal-on-metal interfaces. While one possible approach to solving this problem would be to remove from the lubricant those components that provide high metal-on-composition friction, this is not necessarily desirable. The additives within such lubricants are usually carefully balanced, so that the removal of one component may affect the performance of the lubricant in unintended ways. Furthermore, it may be undesirable, from a commercial standpoint, to stock multiple complete motorcycle lubricants: some for motorcycles with a wet clutch, and some for motorcycles with a dry clutch.
Various friction-reducing additives are known. Glycerol monooleate (“GMO”) is a well-known friction modifier for engines as disclosed in, e.g., U.S. Patent Publication 2008-0280795, Fujitsu, Nov. 13, 2008. However, GMO does not appear to be particularly effective in the present application. Various molybdenum compounds are also known as friction modifiers, as disclosed in, the aforementioned US 2008-0280795. However, Mo compounds are relatively expensive and thus may be impractical at the concentrations that may be required to achieve the desired effect in the present application.
Various materials are known as friction modifiers or friction stabilizers in the context of lubrication of automatic transmissions, that is, devices that do involve lubrication of a wet clutch. U.S. Pat. No. 5,344,579, Ohtani et al., Sep. 6, 1994, discloses a friction modifier system with the capability of establishing and maintaining a substantially constant static breakaway coefficient of friction between a pair of friction surfaces. The additive the composition comprises (a) a hydroxyalkyl aliphatic imidazoline in which the hydroxyalkyl group contains from 2 to about 4 carbon atoms, and in which the aliphatic group is an acyclic hydrocarbyl group containing from about 10 to about 25 carbon atoms, and (b) a di(hydroxyalkyl) aliphatic tertiary amine. A particularly preferred compound is said to be 1-hydroxyethyl-2-heptadecenyl imidazoline.
U.S. Patent Publication 2008/0051306, Chasan et al., Feb. 28, 2008, discloses a lubricant composition containing sterically hindered amine compounds as antioxidants. The lubricants disclosed are said to be functional fluids, that is, lubricants, hydraulic fluids, or metal working fluids. The antioxidants are said to be of particular importance, in that, for instance, oxidative degradation of lubricants plays a significant role especially in motor oils because of the high temperature prevailing in the combustion chamber of the engines. Various other additives may be present, including, for instance, as examples of rust inhibiters and friction modifiers: nitrogen-containing compounds, for example: heterocyclic compounds, for example: 2-heptadecenyl-1-(2-hydroxyethyl)imidazoline.
The disclosed technology, therefore, solves the above problems by providing a top-treatment of an additive which can effectively convert a traditional motorcycle lubricant into one having improved (reduced) metal-on-metal friction and resulting improved fuel economy. The top-treatment may be added by the consumer, by a retailer, or by the manufacturer. The resulting lubricant provides a desired reduction in friction coefficient which is typically reflected by an increase in fuel economy. The disclosed technology may also be used to lubricate internal combustion engines generally (that is, not exclusively motorcycle engines).